Tiopental altera a resposta nociceptiva de ratos jovens em longo prazo / Thiopental alters long term nociceptive response of young rats

The objective of this study was to evaluate the long term nociceptive response determined by use of two general anesthetics, one intravenous and the other inhalatory, in young animals. In the first experiment, the animals of 21 days of age were divided into control (saline) and thiopental (35 mg/kg, i.p.) groups. In the second experiment, rats of the same age were divided in two groups ­ halothane (2%) and control. In experiment 1, there was difference between groups ­ reduction of tail-flick latency in the group thiopental (P< 0.05). In experiment 2, there were no differences between groups or interaction between time versus group (F(1,19)=0.11 for groups, P>0.05; F(1,19)=0.032 for the interaction, P>0.05). The results obtained in this study showed that halothane did not alter the nociceptive response in young animals. However, the thiopental induced hyperalgesic response in rats. (AU)

O objetivo desse estudo foi avaliar a resposta nociceptiva a longo prazo relacionada ao uso de dois anestésicos gerais ­ um intravenoso e outro inalatório, em animais jovens. No primeiro experimento, os animais de 21 dias de idade foram divididos nos grupos controle (solução salina) e tiopental sódico (35 mg/kg, i.p.). No segundo experimento, animais de mesma idade foram divididos em dois grupos ­ halotano (2%) e controle. No Experimento 1, houve redução da latência de retirada da cauda no grupo tiopental (P<0,05). No Experimento 2, não houve diferença entre os grupos ou interação entre grupo x tempo (F(1,19)=0,11 para grupos, P>0,05; F(1,19)=0,032 para a interação, P>0,05). Os resultados obtidos nesse estudo demonstraram que o halotano não altera a resposta nociceptiva em animais jovens. Entretanto, o tiopental induziu resposta hiperalgésica nestes ratos.(AU)

NMDA-receptor-dependent, muscimol-sensitive role of the entorhinal cortex in post-training memory processing.

The bilateral infusion into the entorhinal cortex of the NMDA receptor antagonist, AP5 (5.0µg) or of the GABA(A) agonist, muscimol (0.03µg) 90min after training but not 30min before training, 0min after training or 10min before testing, hindered retention test performance 24h after inhibitory avoidance in rats. Glutamate (5.0µg) or picrotoxin (0.08µg) infused 90min after training had no effect. In animals trained with a low level footshock a second training session, 120min after the first, was needed in order to obtain a good retention test performance. This was taken to reflect summation of the consecutive memory traces left by the two training sessions. In these animals, the infusion of AP5 or muscimol into the entorhinal cortex between the two training sessions impeded their summation. The present results suggest that the entorhinal cortex plays a late role in memory processing, that this role does not need a hyperactivation of the entorhinal cortex, and that it is important for the interaction between consecutive memory traces.